Juan Eduardo Cirlot wrote in his Dictionary of Symbols:
The last sign of the Zodiac, closely bound up with the symbolism of water and of the ‘dissolution of forms’ which takes place in the Akasha. Neptune whipping up the waves with his trident, and calling forth bulls and horses out of them, is a symbolic expression of the resurgence of cosmic energy from the watery deeps of the primordial ocean. If Capricorn marks the beginning of the process of dissolution, Pisces denotes the final moment which, for this very reason, contains within itself the beginning of the new cycle. Related to Pisces are the avatar in the form of the fish of Vishnu in India, and the Chaldean myth of Oannes the man-fish. This twelfth house of the Zodiac, when transposed, by analogy, to the existential and psychic plane, denotes defeat and failure, exile or seclusion, and also mysticism and the denial of the self and its passions. The dual aspect of this symbol is well expressed by the zodiacal sign itself, composed of two fishes arranged parallel to one another but facing in different directions: the left-hand fish indicates the direction of involution or the beginning of a new cycle in the world of manifestation, while the fish that faces the right points to the direction of evolution — the way out of the cycle.Incidentally, Pisces was the first Latin zodiac name that I learned 40 years ago, thanks to the song by Livin’ Blues.